In conventional fashion, a ski brake comprises one, and preferably two, brake arm, which move between an operative braking position, in which they project outward beneath the lower ski surface, and a non-operative resting position, in which they are folded back above the upper ski surface. In the non-operative position, the brake arms are, moreover, advantageously drawn back toward the longitudinal is of the ski, in order to avoid the risk of catching in the snow or with the other ski during skiing.
Moreover, an elastic return means draws the brake arms back into their operative braking position, in particular in order to bring the arms back into the operative position as soon as the boot has been released.
In general, the brake arms are jointed around a transverse pin borne by a base attached to the ski or to the binding base plate. The arms are, furthermore, extended beyond the base, and a device such as a pedal or roller is connected to the extensions of these arms. This device acts on the extensions and on the brake arms, which they cause to be raised then the boot is engaged in the position-retention elements.
In some brakes, the spring is formed by a loop of metal wire possessing a high degree of elasticity and on which stress is generated to deform it, mainly by twisting it. This brake is, for example, described in the DE-DOS number 24 12 623.
This brake gives good results, but proves disadvantageous because its construction is not very economical. In fact, it incorporates a large number of components, since the spring is separate, and, moreover, at a distance, from the brake arms.
In other brakes, the return spring is made of a loop of the same wire as that employed for the arms. That is, the brake arms and the spring form a single component. This brake is described, for example, in DE-OS 25 54 110 with reference to the embodiment illustrated in FIGS. 1, 2 and 5. This brake has a metal wire folded so as to form an "M" shape. The legs of this "M" constitute the brake arms and are mounted so as to pivot around a transverse pin. In side view, the central portion of the "M" forms an angle with the plane of the brake arms, and its lower portion is supported on the base or on a block fastened to the latter. When the brake arms are placed in the non-operative position, the central portion of the "M" is forced to re-enter the plane of the brake arms, thereby giving rise to a return force caused by the deformation of the wire.
The brake has the advantage of a very simple, reliable structure. However, its disadvantage results from the fact that the stiffness of the return spring is dictated by the wire used for the brake arms, or vice-versa.
In other words, the brake arms advantageously possess a slight deformation capability, so as to damp the jolts produced in the active braking phase.
From another perspective, the return spring elastically opposes the rising motions of the brake arms, and then, if required, the return movements of the brake arms toward the longitudinal axis of the ski.
In the case of a brake like that described in DE-OS 25 54 110, it is not possible to control individually the inherent elasticity of the brake arms on one side, and the stiffness of the return spring and of the return movement of the spades on the other side. In fact, this is the same wire which forms the three brake components.
Another disadvantage lies in the design of the base and in the assembly of the "M"-shaped wire to the base. In fact, the base is subjected to pronounced stresses because the spring is made using the same wire as that employed for the brake arms, and that, accordingly, relative stiff. Furthermore, the base must make possible the assembly of the "M"-shaped loop in its entirety.